1. Technical Field
The present invention relates to a safety apparatus for a portable gas range, and more particularly, to a safety apparatus, by which safety measures are conducted before an internal pressure of a canister is rapidly increased to an abnormal high pressure due to radiant heat or the like in use to prevent the canister from being overheated and thus obviate a resulting explosion of the canister. Also, the present invention relates to a method for operating the safety apparatus.
2. Discussion of the Related Art
A common portable gas range includes, as shown in FIG. 1, a burner 50 with an igniter, a device 51 for mounting/demounting a canister 55 to or from the gas range, a canister receptacle 53 having a gas inlet to be coupled to the canister 55 and a regulator 52 for controlling the discharge of a gas supplied to the burner 50 through the gas inlet, and a case 54 for enclosing and securing the components. The burner 50 is adapted to be connected to the regulator 52 via an air mixing pipe (indicated by reference numeral 103 in FIG. 7)
Such a portable gas range is widely used to easily cook food in indoors or outdoors, because of their light weight and convenient portability. The canister (i.e., gas container) contains therein butane gas under a gas pressure of 2 kg/kg/cm2 to 3 kg/cm2 (2 kg/cm2 for Japan). Consequently, the canister is always attended by the risk of a safety accident, such as explosion or fire, caused by a careless user or external thermal source (for example, radiant heat).
It is described in a provision of Korean LPG Safety Control Act a gas container must have a safety apparatus capable of automatically cutting off a gas supply in a pressure range of 5 kg/kg/cm2 to 7 kg/kg/cm2, which is regarded as a danger pressure, when the internal pressure of the gas container is rapidly increased to the abnormal high pressure, in order to prevent the safety accident.
A typical safety apparatus comprises a detachable safety apparatus, by which when the internal pressure of the gas container is increased in a pressure range of 5 kg/cm2 to 7 kg/cm2 (4 kg/cm2 to 6 kg/cm2 for Japan), which is regarded as a danger pressure below an explosion critical pressure, the gas supply is interrupted by automatically releasing the gas container from the gas inlet using the increased pressure, and a flow path cutoff safety apparatus, by which when the internal pressure of the gas container is increased in a pressure range of 5 kg/cm2 to 7 kg/cm2, which is regarded as a danger pressure, a gas flow path formed in a regulator is automatically interrupted by the increased pressure to stop the gas supply.
The detachable safety apparatus is adapted to operate in cooperation with the canister attaching/detaching device installed to the canister receptacle of the gas range and a safety rod received in a housing under the regulator.
A prior art detachable safety apparatus will now be described in detail with reference to FIGS. 1 and 2.
The canister mounting/demounting device 51 slidably mounts/demounts the canister 55 to/from the gas inlet of the regulator 52, and includes a canister receptacle 53 for receiving the canister 55, an operating link 58 with one end portion protruded outwardly from the canister receptacle 53 and engaged to a partition 56 in the burner 50 by a hinge axis 57 to for a handle 58a and the other end portion formed with a guide groove 58b, and a slide link 59 with one end portion engaged to the guide groove 58b and the other end portion formed with seat 59a and slidably moved thereon. A compression spring 60 is installed to the operating link 58 using the partition 56 as a supporting point.
When a user pushes down the handle 58a, as shown in FIG. 2A, with the canister 55 seated on the canister receptacle 53, the compression spring 60 is stretched, such that the canister 55 is moved toward the operating link 58 by the slide link 59 to engage with the gas inlet of the regulator 52. In this state, the operating link 58 is moved upward, and the seat 59a is moved backward together with the slide link 59 by a restoring force of the compression spring 60, such that the canister 55 is detached from the gas inlet.
A releasing lever 61 is hingedly engaged to the partition 56 at a lower position of the operating link 58.
As such, the safety rod 62 which is resiliently installed in the housing 52a at a lower position of the regulator 52 by a resilient spring (not shown) is adapted to automatically detach the canister 55 in cooperation with the releasing lever 61, when the internal pressure of the canister 55 is increased to the abnormal high pressure.
Specifically, the canister 55 is engaged to the gas inlet of the regulator 52, in use. If the canister 55 is overheated and thus the gas pressure reaches a level of 5 kg/kg/cm2 to 7 kg/kg/cm2, the safety rod 62 automatically protrudes from the lower portion of the housing 52a by the increased pressure to push one end portion of the releasing lever 61 displaced under the safety rod. At this time, the other end portion of the releasing end portion 61 is moved upward to lift the operating link 58 upwardly. In result, the slide link 59 is moved backward by the restoring force of the compression spring 60, such that the canister 55 is automatically detached from the gas injection port of the regulator 52, thereby interrupting the gas supply to the burner 50 and thus preventing the explosion of the canister.
With the conventional detachable safety apparatus, only when the gas pressure introduced into the regulator through the gas inlet reaches the level of danger pressure, 5 kg/cm2 to 7 kg/cm2, in the state where the canister is overheated, the safety rod is adapted to interrupt the gas supply. Consequently, the safety apparatus cannot prevent the overheating of the canister. In other words, the safety apparatus operates immediately before the canister blows up. Therefore, there is a problem in that the apparatus still contains a radically accident danger such as explosion or fire.
FIGS. 3A and 3B are a side cross-sectional view and a front cross-sectional view illustrating one example of a conventional flow path cutoff safety apparatus, respectively.
As shown in FIGS. 3A and 3B, the flow path cutoff safety apparatus includes a gas inlet 70 detachably engaged to a canister 55, a chamber 71 for keeping a gas pressure supplied to a burner at a constant level, and an adjusting lever 72 for adjusting an amount of the gas supplied to the burner. Gas cutoff means 73 is installed in a gas flow path defined by the gas inlet 70 and the chamber 71, and cuts off the gas flow path when the gas pressure is increased to a predetermined level. The chamber 71 is provided with pressure regulating means 74 for regulating the gas pressure supplied to the burner at a constant level.
The gas cutoff means 73 includes a tapered hole 75 gradually decreased in diameter from the gas flow path to a rear, a cylinder hole 76 straightly communicated with the tapered hole 75, a breaking valve 77 installed in the tapered hole 75 and the cylinder hole 76 and moved rearward by the gas pressure, and a leaf spring 78 biasing a rear of the braking valve 77.
The leaf spring 78 is adjoined a return valve 79 with one end portion exposed outwardly. A return lever 80 is installed on an upper portion of the exposed end, and is slid up and down to push the return valve 79 forwardly.
The breaking valve 77 includes a cutoff portion 81 displaced at a front of the tapered hole 75 and an operating portion 82 displaced at the cylinder hole 76. The cutoff portion 81 is provided on an outer periphery thereof with an O-ring for sealing the tapered hole 75 when it is moved rearward. The operating portion 82 is provided on an outer periphery thereof with O-ring for preventing leakage of the gas pressure. In addition, a nozzle hole 83 is formed at one side of the cylinder hole 76 at the front of the operating portion 82, and is communicated with the nozzle hole 83.
The pressure regulating means 74 includes a rubber plate 83 installed to an upper portion of the chamber 71 to seal the chamber, a spring 85 for urging the rubber plate 84 downwardly, a needle holder 86 connected to the rubber plate 84, and a needle valve 88, of which a center portion is hingedly engaged to a body in such a way that one end portion of the needle valve is engaged to the needle holder 86 and the other end portion is provided with a stopper 87. Reference numeral 89 denotes a support secured to a bottom surface of the canister receptacle.
As such, when the user ignites the gas range, the gas filled in the chamber 71 is supplied to the burner, and the gas pressure in the chamber 71 is lowered. Then, the rubber plate 84 is pushed down by the spring 85, such that the needle valve 88 hingedly engaged to the regulator 52 is spaced apart from the nozzle hole 83 to introduce the gas from the canister to the chamber 71. If the gas pressure introduced into the chamber 71 is increased to a predetermined level, the rubber plate 84 is lifted up against the biasing force of the spring 85 to rotate the needle valve 88 and thus cutoff the nozzle hole 83. In addition, when the gas pressure is increased to a predetermined level due to the overheating of the canister 55, the breaking valve 77 installed to the gas flow path is moved backward against the biasing force of the leaf spring 78 by the gas pressure to close the tapered hole 75, so that the gas supply is interrupted to put out a flame of the burner.
However, according to the conventional flow path cutoff safety apparatus shown in FIG. 3, it is required to precisely machine related components to completely cutoff the gas flow path. If it is not precisely machined, an accident may occur. In addition, even though the related components have been precisely machined, the gas remains in the cutoff gas flow path. Consequently,there is a serious problem in that the canister may explode in the case the canister is overheated.
In order to solve the above problem, an improved flow path cutoff safety apparatus is disclosed in Korean Patent Unexamined Publication No. 2001-0008025, in which when the gas pressure is increased to a predetermined level due to the overheating of the canister, the gas in the canister is outwardly discharged, so as to prevent the explosion of the canister.
FIG. 4 is a front cross-sectional view of a conventional flow path cutoff safety apparatus.
As shown in FIG. 4, a gas discharging means 90 includes a cylinder hole 91, a through hole 92 formed at one side of the cylinder hole 91 to communicate with a gas flow path, a housing 94 provided at a circumferential surface of the through hole 92 with a discharging hole 93 for discharging outwardly the gas flowed toward the through hole 92, and a safety rod 96 resiliently supported by a spring 95 to be closely adjacent to the through hole 92. A disc-shaped cap 97 is threadedly engaged to one end portion of the housing 94, and a nozzle 98 outwardly extended is engaged to the discharging hole 93.
With the construction as described above, if the chamber 71 is filled with the gas above a predetermined level of pressure, the nozzle hole 83 is cut off by the needle valve 88 of the pressure regulating means 74 so as to primarily interrupt the gas to be supplied to the chamber 71, as described above with reference to FIG. 3. In this cutoff state, if the gas pressure is continuously increased above a predetermined level due to the overheating of the canister, the gas supply is secondarily cut off by the operation of the gas cutoff means 73 to put out a flame of the burner.
In this circumference, even though a fire breaks out around the gas range or the gas pressure is increased to above predetermined level, for example, 13 kg/cm2 to 15 kg/cm2, due to the latent heat accumulated in the gas range or canister, the safety rod 96 of the gas discharging means 90 is moved backward against the biasing force of the spring 95 to open the through hole 92, so that the gas in the canister is outwardly discharged through the nozzle 98. Therefore, even though the canister is continuously overheated, it does not explode.
However, the flow path cutoff safety apparatus has some problems as follows:
First, the housing 94 provided with the safety rod 96 extends from the tapered hole 75 and protrudes from the side of the regulator 52 such that the through hole 92 is opened or closed by the safety rod 96 operated by the spring 95. Therefore, the volume of the regulator is increased, and moreover the construction is complicated. In addition, since the internal structure of the general portable gas range is remarkably altered, its productivity is lowered and its manufacturing cost is increased.
Second, since the discharging hole 93 is formed in the interior of the regulator, a separate nozzle 98 has to be provided to discharge the gas outwardly.
Third, since the gas is discharged outwardly through the discharging hole 93, there is a problem of causing a secondary fire accident in the case where flammable gas is displaced in the vicinity of the gas range via nozzle 98.
Finally, as similar to the prior art related with FIG. 3, it is necessary to precisely machine the related components in order to completely cut off the gas flow path.